Gamma rays from violent supernovae explosions interact with atoms in the upper atmosphere of the earth. Primary gamma-nucleon interactions produce relativistic pions, and kaons which travel over 120 km before decaying into neutrinos and muons. The relativistic muons, or cosmic rays, minimally interact with matter and often travel through the Earth. Cosmic ray studies reveal that 80% of the particles which reach terrestrial levels are muons. FIG. 1 is a graph showing stratifications of the atmosphere from the ionosphere to the earth where approximately 80% of the cosmic particles that reach terrestrial levels are muons.
The goal of experimental high energy physics is to identify the fundamental constituents of matter through measurement of the particle velocity, momentum, and energy loss due to ionization of atoms in the detector medium. Cerenkov detectors use ultraviolet photons from the Cerenkov effect and the index of refraction of the detector medium to determine particle velocity. Electromagnetic or hadronic calorimeters are used to identify particle mass and the ionization energy loss in the particular detector medium. We present the Threshold Cerenkov Detector with Radial Segmentation (TCDRS) which is designed to measure the particle velocity, mass and consequently the momentum within the same detector volume.
One device that has been useful in particle identification studies is a Cerenkov radiator (FIG. I):
The radiator has a cylinder with windows at both ends and an enclosed pressurized gas chamber. A charged relativistic, subatomic particle enters one window, along the body axis of the cylinder in a direction parallel to the body axis, and passes through the gas so as to produce transient flashes of faint predominantly blue Cerenkov light. The light is a function of the well known Cerenkov relation cos θ=1/(nβ) where n corresponds to the refractive index of the gas and β corresponds to the velocity of the particle in the medium divided by the speed of light in a vacuum. The light flashes have passed through the opposite end window and reflected at a suitable angle, such as a forty-five degree angle away from the particle path toward a counting device, for example multi-channel ADCs and a data acquisition system.